The present invention relates to a durable accommodating intraocular lens (IOL) and a method for making and using the same. More particularly, the present invention relates to durable flexible attachment components for an accommodating IOL designed for multi-distance visual imaging in aphakic eyes where a natural lens has been surgically removed, such as in the case of cataracts.
Intraocular lens (IOL) implants have been used for many years in aphakic eyes as replacements for natural crystalline lenses that have been surgically removed from the eyes. Many different IOL designs have been developed over past years and proven successful for use in aphakic eyes. Successful IOL designs to date primarily include an optic portion with supports therefor, called haptics, connected to and surrounding at least part of the optic portion. The haptic portions of an IOL are designed to support the optic portion of the IOL in the lens capsule, anterior chamber or posterior chamber of an eye.
Commercially successful IOLs have been made from a variety of biocompatible materials, ranging from more rigid materials such as polymethylmethacrylate (PMMA) to softer, more flexible materials capable of being folded or compressed such as silicones, certain acrylics, and hydrogels. Haptic portions of the IOLs have been formed separately from the optic portion and later connected thereto through processes such as heat, physical staking and/or chemical bonding. Haptics have also been formed as an integral part of the optic portion in what is commonly referred to as xe2x80x9csingle-piecexe2x80x9d IOLs.
Softer, more flexible IOLs have gained in popularity in more recent years due to their ability to be compressed, folded, rolled or otherwise deformed. Such softer IOLs may be deformed prior to insertion thereof through an incision in the cornea of an eye. Following insertion of the IOL in an eye, the IOL returns to its original pre-deformed shape due to the memory characteristics of the soft material. Softer, more flexible IOLs as just described may be implanted into an eye through an incision that is much smaller, i.e., 2.8 to 3.2 mm, than that necessary for more rigid IOLs, i.e., 4.8 to 6.0 mm. A larger incision is necessary for more rigid IOLs because the lens must be inserted through an incision in the cornea slightly larger than the diameter of the inflexible IOL optic portion. Accordingly, more rigid IOLs have become less popular in the market since larger incisions have been found to be associated with an increased incidence of postoperative complications, such as induced astigmatism.
After IOL implantation, both softer and more rigid IOLs are subject to compressive forces exerted on the outer edges thereof from natural brain-induced contraction and relaxation of the ciliary muscles and increases and decreases in vitreous pressure. Compressive forces of this kind are useful in a phakic eye for focusing the eye at various distances. Most commercially successful IOL designs for use in aphakic eyes have single focus optic portions that are fixed and focus the eye at only a certain fixed distance. Such fixed single focus IOLs require the wearing of glasses to change the focus of the eye. A few fixed bifocal IOLs have been introduced to the commercial market but suffer from the disadvantage that each bifocal image represents only about forty percent of the available light thus lessening visual acuity. Accommodating IOLs designed to have two optics held together by flexible loops or straps have also been proposed. However, the flexible attachment components of accommodating IOLs must flex millions of times during a patient""s lifetime. Very few materials can withstand such stresses in an aqueous environment without cracking and failing.
Because of the noted shortcomings of current IOL materials, there is a need for an IOL material capable of providing the rigidity required for supporting an IOL optic, capable of being manufactured into small dimensions to fit into the required anatomical space of an eye and capable of withstanding the stresses of accommodation overtime in an aqueous environment without cracking and failing.
The present invention is the use of polyurethane elastomers to manufacture flexible attachment components for accommodating intraocular lenses (IOL). Although the polyurethane elastomer flexible attachment components of the subject invention may be used for durable function and support in any suitable accommodating IOL design, for purposes of explanation not limitation, particular accommodating IOL designs are described herein. In one accommodating IOL design, the polyurethane elastomer flexible attachment components of the present invention are used to permanently or removably attach preferably a positive IOL optic to a negative IOL optic. The positive IOL optic has a xe2x80x9chigherxe2x80x9d diopter, preferably approximately +20 diopter or greater, such as but not limited to +20 to +60 diopter, with an outer peripheral edge and two or more but preferably two, three or four polyurethane elastomer flexible attachment components for durable support and function within a patient""s eye. The negative IOL optic has a xe2x80x9clowerxe2x80x9d diopter, preferably approximately xe2x88x9210 diopter or less, such as but not limited to xe2x88x9210 to xe2x88x9250 diopter, also with an outer peripheral edge and preferably the same, but optionally a different number of polyurethane elastomer flexible attachment components from that of the positive optic portion. Positive and negative IOL optics each having two polyurethane elastomer flexible attachment components are balanced for stability within an eye to minimize decentration by having the flexible attachment component integrally formed with or subsequently attached to two opposed edges of each of the two optic portions. Positive and negative IOL optics each having three polyurethane elastomer flexible attachment components are balanced to achieve stability and minimize decentration by having a set of two flexible attachment components integrally formed with or subsequently attached to one edge of each of the optic portions and a third flexible attachment component integrally formed with or subsequently attached to an opposite edge of each of the optic portions. Positive and negative IOL optics each having four polyurethane elastomer flexible attachment components are balanced to achieve stability and minimize decentration by each optic portion having a set of two flexible attachment components integrally formed with or subsequently attached to one edge of the optic and a set of two flexible attachment components integrally formed with or subsequently attached to an opposite edge of the optic. Each polyurethane elastomer flexible attachment component has an attachment portion that permanently connects the flexible attachment component to the outer peripheral edge of an optic portion. If the flexible attachment component is of a looped design, the flexible attachment component has generally two attachment portions that permanently connect the looped flexible attachment component to the outer peripheral edge of the optic portion. In the case of lenses having three or four looped flexible attachment components, a set of two looped flexible attachment components may have three attachment portions rather than four. In such a case, one of the three attachment portions is common to each of the two looped flexible attachment components in the set. Each polyurethane elastomer flexible attachment component whether of a loop design or not includes a flexible central portion located between the attachment portion and a contact plate. The contact plate is designed to engage an inner surface of a patient""s eye. The flexible central portions that extend between the contact plates and the attachment portions allow the optic portions of both the positive and negative IOLs to move or to adjust to pressures exerted on the positive and negative lenses within the eye. Additionally, within these flexible central portions, each polyurethane elastomer flexible attachment component is designed to have less resistance to bending in a plane generally parallel to the optical axis of an eye than in a plane generally perpendicular to the optical axis of an eye. By providing polyurethane elastomer flexible attachment components with significantly superior flexibility and durability characteristics, accommodating IOLs are capable of providing accommodative visual effects throughout a patient""s lifetime.
Accordingly, it is an object of the present invention to provide flexible and durable accommodating IOLs for use in aphakic eyes.
Another object of the present invention is to provide accommodating IOLs for use in aphakic eyes having flexible and durable attachment components.
Another object of the present invention is to provide a durable material for use in the manufacture of accommodating IOLs.
Another object of the present invention is to provide accommodating IOLs for use in aphakic eyes, which are relatively easy to manufacture.
Still another object of the present invention is to provide accommodating IOLs, which are durable and resistant to decentration within the eyes.
These and other objectives and advantages of the present invention, some of which are specifically described and others that are not, will become apparent from the detailed description, drawings and claims that follow, wherein like features are designated by like numerals.